1. Technical Field
Embodiments of the present invention relate to an adhesive composition for polarizing plates, an adhesive film using the same, a polarizing plate including the same, and an optical display including the same.
2. Description of the Related Art
A liquid crystal display includes a polarizing plate stacked on each surface of a liquid crystal display panel. The polarizing plate includes a polarizer and a protective film formed on each surface of the polarizer. The polarizing plate may be stacked on the liquid crystal display panel via an adhesive layer formed on one surface of the protective film. A polarizing plate with a protective film formed on only one surface of the polarizer (referred to as a “TAC-less” polarizing plate when the protective film is a triacetyl cellulose (TAC) film) can lead to reduced material costs while still having a small thickness.
Such a TAC-less polarizing plate (in which a protective film is formed on only one surface of the polarizer) is likely to have a high warpage value and exhibit poor durability and reliability. In order to enhance durability and reliability, an adhesive layer may include a (meth)acrylic copolymer obtained by polymerization of a monomer mixture including a carboxylic acid group-containing monomer. However, such an adhesive layer can cause corrosion of the metal coating (due to the carboxylic acid group) when used in an indium tin oxide (ITO) metal-coated plane-to-line switching (PLS) or in-plane switching (IPS) liquid crystal panel.
Further, since the polarizer directly adjoins the adhesive layer in such a TAC-less polarizing plate, adhesion between the polarizer and the adhesive layer must be ensured in order to provide re-workability. However, the typical adhesive layer is limited in its ability to enhance adhesion between the polarizer and the adhesive layer. In addition, since the polarizer directly adjoins the adhesive layer in a TAG-less polarizing plate, the polarizer is likely to suffer from cracking under harsh conditions (such as high temperature and/or high humidity environments). In order to overcome these problems, the adhesive layer must have sufficient adhesion to the polarizer. As described above, however, the typical adhesive layer has limited ability to enhance adhesion between the polarizer and the adhesive layer.